The aims of this project are to elucidate the pathogenesis of idiopathic nocturia in elderly people. Specifically, we plan to test the hypothesis that idiopathic nocturia is caused by one of the following: a)nocturnal abnormalities in the bladder tone or the activity of the external sphincter, b)sleep apnea or hypopnea and c)nocturnal deficiencies of vasopressin, aldosterone or both hormones, which result in nocturnal urine outputs greater than the functional capacity of the bladder.